An immunochromatography is a diagnostic method using nanoparticles. Being simple to operate and requiring relatively short time of approximately 5 to 30 minutes for determination and no expensive devices, it is widely used as an excellent simple diagnostic method in actual clinical scenes. For example, for determination of influenza virus infection, by having a pharynx cotton swab or nasal cavity cotton swab collected from a patient as an analyte, the determination can be made on site within a short time, and thus it is used as a very dominant tool for quick determination of infection.
Colored particles such as gold colloid or colored latex particles are generally used as labeling particles for the immunochromatography. In some cases, the sensitivity of immunochromatography using such colored particles is insufficient, depending on the condition or amount of the analyte or the measurement item. Moreover, the result may be false positive or false negative, which can be a cause of misdiagnosis and the like. For solving these problems, it has been tried to achieve highly sensitive immunochromatography.
The applicant has proposed methods for increasing the sensitivity of immunochromatography, which include fluorescent immunochromatography using fluorescent particles or using fluorescent particles in combination with light absorbing particles (see Patent Literatures 1 to 3). Using the proposed techniques, fluorescence emitted from the test area can be detected not only visually but also with an optical receiver for high accuracy or convenience of quantitative measurement. For a high-sensitivity detection device suitable for use in this measurement, the applicant has previously proposed a technique using a specific lens system as disclosed in Patent Literature 4.